A Preliminary Study of Vortex Formation from Pulsed Jets,
GEORGE WASHINGTON UNIV WASHINGTON D C DEPT OF CIVIL MECHANICAL AND ENVIRONMENTAL ENGINEERING
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It is known that superior thrust augmentation may be obtained in ejectors by the use of pulsed jets as opposed to steady flow jets. Pulsed jets and other unsteady flow devices offer the advantage that they can capitalize on the reversible work of interface pressure forces as well as the usual irreversible turbulent mixing. The latter alone is employed in steady flow ejectors. When a pulsed jet discharges into a duct or an open environment, the jet forms a toroidal vortex ring which acts as a piston pushing the ambient fluid in its path. The configuration of this vortex ring can be extensively controlled by proper control of the boundary conditions at the exit of the jet. The present work is a preliminary study of the configurations of the vortex rings produced by different boundary conditions and of their subsequent behavior. It is hoped that such a study will illuminate some avenues of improvement for pulsed-jet ejector technology.